1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer and the like, a unit detachably attachable to such an image forming apparatus, and a developer remaining amount displaying system, and more particularly, it relates to an image forming apparatus capable of displaying a remaining amount of developer correctly, a unit detachably attachable to such an image forming apparatus, and a developer remaining amount displaying system.
2. Related Background Art
In conventional electrophotographic image forming apparatuses such as electrophotographic copying machines, laser beam printers and the like, a latent image is formed by illuminating light corresponding to image information onto an electrophotographic photosensitive member, and the latent image is visualized as a developer image by supplying developer to the latent image from developing means, and an image is formed on a recording medium by transferring the developer image from the photosensitive member to the recording medium. A developer containing container as a developer containing portion is connected to the developing means, and the developer is consumed as the image is formed.
In such an image forming apparatus, for the purpose of facilitating exchanging consumed parts such as the electrophotographic photosensitive member and the developer and maintenance, there has been proposed a process cartridge in which an electrophotographic photosensitive member and process means (such as developing means, electrifying means and/or cleaning means) and a developer containing container and a waste developer container are integrally incorporated as a cartridge unit which is detachably attachable to a main body of the image forming apparatus. According to such a process cartridge, since the maintenance of the apparatus can be performed by an operator himself without any expert, operability can be enhanced remarkably. Thus, the process cartridge has widely be used in the electrophotographic image forming apparatus.
Further, for example, in a color image forming apparatus having a plurality of color developing means, when consumed degrees of respective developing means are different, the respective developing means and the corresponding developer containing containers may be incorporated as respective color developing cartridges which are independently detachably attachable to the main body of the image forming apparatus.
In an image forming apparatus of a cartridge type, for example, when the developer is exhausted, by exchanging the cartridge with a new one by the operator, image formation can be performed again. To this end, the image forming apparatus may have means for detecting consumption of the developer and for notifying the result to the operator.
In order to always know the amount of developer (to be used for image formation) remaining in the cartridge, the cartridge or the main body of the image forming apparatus is provided with developer remaining amount detecting means capable of detecting a developer remaining amount level.
Particularly, there is a technique in which the convenience to the operator is further enhanced not only by notifying consumption (exhaustion) of the developer to the operator but also by successively detecting and notifying the remaining amount of developer. Among image forming apparatuses including such a technique, there is an image forming apparatus in which the percentage of the developer remaining amount regarding non-used developer is calculated and the calculated amount is successively noticed to the user or a xe2x80x9cno developerxe2x80x9d condition indicating the fact that the developer is decreased to the extent that image formation having a predetermined image quality cannot be achieved is displayed, thereby informing the user of an insufficient developer remaining amount before a poor image is generated.
As means for detecting the developer remaining amount, there is a system in which at least a pair of input and output electrodes are provided and the developer amount is detected by measuring electrostatic capacity between these electrodes. As one of such developer remaining amount detecting means of electrostatic measurement type, there is a plate-antenna type.
Regarding the plate-antenna type, for example, in a cartridge utilizing a developing system for developing a latent image formed on an electrophotographic photosensitive member by applying AC bias to a developer carrying member of developing means, a metal plate as an electrode is provided in a confronting relationship to the developer carrying member or plural metal plates are provided at other plural locations, and the developer amount is detected by utilizing a property that electrostatic capacity between the metal plate and the developer carrying member or between the metal plates is varied with the amount of developer (insulative toner) therebetween.
That is to say, if the space between the metal plate and the developer carrying member or between the metal plates is filled with the developer, the electrostatic capacity therebetween becomes great, and, as the developer is decreased, air in the space Is gradually increased to decrease the electrostatic capacity. Accordingly, so long as a relationship between the electrostatic capacity between the metal plate and the developer carrying member or between the metal plates and the developer amount is previously sought, the developer amount can be detected by measuring the electrostatic capacity.
The measurement of the electrostatic capacity is effected by measuring electrical current flowing through the metal plate when the AC bias is applied to the developer carrying member or by measuring electrical current flowing through one of the plural metal plates when the AC bias is applied to the other (electrode) of the plural metal plates. Namely, in the developer remaining amount detecting means of plate-antenna type, in many cases, the developer amount is detected during image formation in which the developing bias is being applied to the developer carrying member.
In the above-mentioned developer amount detecting means of electrostatic capacity type, a relationship between the electrostatic capacity detected by the developer remaining amount detecting means and the developer amount is previously sought, and the amount of the developer can be determined from a table or calculation based on such relationship and a detected value of the electrostatic capacity.
However, in the system for detecting the remaining amount of the developer by utilizing the electrostatic capacity, even when developer remaining amount detecting means having the same construction is used and the remaining developer amount (weight) is the same, due to dispersion in distribution of the developer along the metal plate for detecting the electrostatic capacity and/or dispersion in density of the remaining developer, it is not always possible to detect the same electrostatic capacity, and, thus a change in electrostatic capacity upon reduction of the developer may be varied or differentiated, with the result that there arises dispersion in transition of a developer remaining amount detection value detected on the basis of the electrostatic capacity.
Such dispersion in distribution and density of the developer remaining in the developer containing container is caused by fluidity of the developer and/or difference in developer amount initially loaded and/or difference in construction of the container.
If the developer amount cannot be detected correctly for the above-mentioned reasons, for example, when a developer amount is estimated to be more than the actual developer remaining amount, in spite of the fact that the developer is decreased to the extent that an image having a predetermined image quality cannot be formed, since the operator erroneously feels that the developer is still remaining, for example, a cartridge to be exchanged cannot be prepared at a proper timing, with the result that a poor image such as a white void image will be generated. On the other hand, when the developer amount is estimated to be less than the actual developer remaining amount, in spite of the fact that the developer is still remaining, the cartridge is exchanged with a new one, with the result that usable developer is discarded, thereby wasting resources.
The present invention aims to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide an image forming apparatus capable of displaying a remaining amount of developer correctly, a unit detachably attachable to such an image forming apparatus, and a developer remaining amount displaying system.
Another object of the present invention is to provide an image forming apparatus capable of informing exchange of a unit at a proper timing, a unit detachably attachable to such an image forming apparatus, and a developer remaining amount displaying system.
A further object of the present invention is to provide an image forming apparatus comprising a developer container for containing developer, developer amount detecting means for detecting an amount of the developer contained in the developer container, and calculating means for calculating a display level of a remaining amount of the developer, and wherein at least the developer container is detachably mountable on a main body of an image forming apparatus as a unit, and further wherein the calculating means calculates the display level on the basis of a detection amount of the developer amount detecting means and predetermined information regarding a developer remaining amount in the container upon generation of a white void image.
A still further object of the present invention is to provide a unit detachably attachable to an image forming apparatus, comprising a memory, and a developer container for containing developer, and wherein the memory stores predetermined information regarding a developer remaining amount in the container upon generation of a white void image.
A further object of the present invention is to provide a developer remaining amount displaying system comprising a first unit which is detachably attachable to a main body of an image forming apparatus and in which developer is loaded, a second unit which is detachably attachable to the main body of the image forming apparatus and in which developer more than that in the first unit is loaded and which can be mounted to the main body of the image forming apparatus in place of the first unit, and a display for displaying a remaining amount of the developer, and wherein, when the second unit is mounted to the main body of the image forming apparatus, the display displays the fact that there is no remaining amount of the developer or the fact that the unit should be changed at a stage that a detection remaining amount of developer remaining amount detecting means is greater than when the first unit is mounted.
A still further object of the present invention is to provide a developer remaining amount displaying system comprising a first unit which is detachably attachable to a main body of an image forming apparatus and in which developer is loaded and which has an agitating sheet for agitating the developer, a second unit which is detachably attachable to the main body of the image forming apparatus and which has an agitating sheet having a longer free length than the agitating sheet of the first unit and which can be mounted to the main body of the image forming apparatus in place of the first unit, and a display for displaying a remaining amount of the developer, and wherein, when the second unit is mounted to the main body of the image forming apparatus, the display displays the fact that there is no remaining amount of the developer or the fact that the unit should be changed at a stage that a detection remaining amount of developer remaining amount detecting means is greater than when the first unit is mounted.
The other objects and features of the present invention will be apparent from the following detailed explanation of the invention referring to the accompanying drawings.